P450: ALDH1A AS A THERAPEUTIC TARGET IN ACUTE MYELOID LEUKEMIA
Authors: Mehak Shaikh, Muhube Yazir, Céline Baier, Andrada Constantineascu, Julie Vackova, Miroslava K. Adamcova, Mileidys Perez-Alea, Meritxell Alberich-Jorda
Journal: HemaSphere (2023)

Background: Acute myeloid leukemia (AML) is a heterogeneous malignancy characterized by a differentiation arrest and accumulation of blasts. Upon initial treatment, most patients exhibit remission, however 50% of all patients who achieved remission relapse over time. We and others have reported that there is an increase in the levels of the enzyme aldehyde dehydrogenase (ALDH1A) in the group of refractory and relapse AML patients, and that high enzymatic activities are associated with drug resistance. ALDH1A oxidizes the toxic aldehydes to carboxylic acids, thus protecting cells from oxidative damage and proteo-toxic stress. DIMATE is an inhibitor of ALDH1A which could be employed to inhibit chemo-resistance in AML. The use of DIMATE in combination with standard of care drugs could promote chemo-sensitivity and provide clinical benefits. Aims: The aims of this study are (1) to determine the effect of ALDH1A inhibition in AML cells, (2) to investigate the synergistic role of DIMATE with other standard of care drugs and (3) to determine the molecular mechanism causing the synergistic effect. Methods: Drug response assay, capillary electrophoresis immunoassay, colony cultures, and murine in-vivo assays. Experiments have been performed using human AML cell lines and murine MLL-AF9 leukemic models. Results: To understand the effect of DIMATE on AML cell lines, we carried out a drug response assay with different concentrations of DIMATE. We observed that AML cells present high sensitivity to DIMATE leading to reduced viability. Next, colony culture assays of MLL-AF9 leukemic cells demonstrated reduced colony forming potential upon inhibition of ALDH1A. Similarly, treatment of MLL-AF9 leukemic mice with DIMATE reduced the leukemic burden. To understand the cause of apoptosis in these cells, we carried out capillary electrophoresis immunoassays. We found that the Noxa/Mcl-1 axis played a major role and there was a time-dependent regulation of pro-apoptotic and anti-apoptotic proteins in response to DIMATE. Following exposure of AML cells to DIMATE, apoptogenic aldehydes accumulated and apoptosis occurred by simultaneous induction of 1) endoplasmic reticulum (ER) stress, 2) the genotoxic stress sensor GADD45 and 3) reactive oxygen species (ROS). DIMATE induction of ER stress condition was verified by the activation of the eiF2a/ATF4/CHOP sensor axis, known to promote apoptosis, and abrogation of the NFkB signaling pathway. In addition, DIMATE also lead to down-regulation of the proliferative AKT/mTOR pathway. Next, we screened the cytotoxic effect of 10 standard of care drugs in combination with DIMATE in a panel of 10 different AML cell lines. The most synergistic interactions were obtained with DIMATE and hypomethylating agents decitabine and azacytidine. The effect of DIMATE in combination with decitabine was further explored using colony forming assays using AML cell lines. Next, the synergistic effects of DIMATE and decitabine were supported using MV411 cells transplanted into NSG-SGM3 mice. Summary/Conclusion: We observed that leukemic cells treated with DIMATE exhibit increased apoptosis, due to upregulation of apoptotic proteins, abrogation of the NFkB signaling pathway, and downregulation of the AKT/mTOR signaling pathway. Further, we determined synergistic effects between DIMATE and hypomethylating agents, which could help in promoting chemo-sensitivity and have a clinical benefit. The work was partially funded by the National Institute for Cancer Research (Program EXCELES, ID Project No. LX22NPO5102) - Funded by the European Union - Next Generation EU. Keywords: Aldehyde dehydrogenase, Acute myeloid leukemia, Hypomethylating agents, Chemoresistance